wound-healing-reading-chapters

SRPS Volume 10, Number 7, Part 1
cell to radiation damage is directly proportional to
its mitotic rate. The most sensitive cells are those
which divide rapidly, such as cells of the skin, bone
marrow, and gastrointestinal tract. In addition to
sensitivity of the exposed cell, morbidity from
radiation depends on the dose received, time over
which the dose is received, volume of tissue irradiated,
and type of radiation. 399 Cellular changes
resulting from low-dose radiation are probably due
to an apoptotic mechanism, whereas changes
related to high-dose radiation are probably due to
direct cellular necrosis.
The direct effects of radiation can be immediate,
acute (days to weeks), or delayed (months to
years). Acute effects result from necrosis of the rapidly
proliferating cell lines. A transient, faint erythema
may appear during the first week of treatment due
to dilation of capillaries and may be associated with
an increase in vascular permeability. Radiation
inhibits mitotic activity in the germinal cells of the
epidermis, hair follicles, and sebaceous glands. Epilation
and dryness of the skin occur. By the third or
fourth week of radiation, typical erythema is localized
to the radiation field and the skin is noticeably
red, edematous, warm, and tender. Larger vessels
may be obstructed by fibrin thrombi, edema is
prominent, and there may be small foci of hemorrhage.
400 Cellular exudate is rare. If the total radiation
dose to the skin does not exceed 30Gy, the
erythema phase is followed during the fourth or
fifth week by a dry desquamation phase characterized
by pruritus, scaling, and an increase in melanin
pigmentation in the basal layer. Within 2 months
the inflammatory exudate and edema have subsided,
leaving an area of brown pigmentation.
If the total radiation dose to the skin is >40Gy,
the erythema phase is followed by a moist desquamation
phase. This stage usually begins in the fourth
week and is often accompanied by considerable
discomfort. Bullous formation occurs above the basal
layer and sometimes just below the epidermis. Eventually
the roofs of the bullae are shed and the entire
epidermis may be lost in portions of the irradiated
area. Edema and fibrinous exudate persist. In the
absence of infection, reepithelization of the
denuded skin usually begins within 10 days. Ulcers
may appear 2 weeks or more after radiation exposure.
These ulcers are a result of direct necrosis of
the epidermis; they usually heal but tend to
recur. 399,401
Approximately 1 year after radiation treatment
the epidermis is thin, dry, and semitranslucent, with
vessels easily seen. Hair follicles and sebaceous
glands are usually absent. Some sweat glands may
also have been destroyed. In time, increasing fibrosis
of the skin is present. Much of the collagen and
subcutaneous adipose tissue are replaced by atypical
fibroblasts and dense fibrous tissue that may
cause induration of the skin and may limit movement.
In radiation injury of soft tissue, fibrinous
exudate accumulates under the epidermis. Characteristic
features of delayed radiation lesions are
eccentric myointimal proliferation of the small
arteries and arterioles as well as telangiectasia. These
changes may progress to thrombosis or complete
obstruction. Delayed ulcers are more common than
acute ulcers and result from ischemic changes in
small arteries and arterioles; they heal slowly and
may persist for several years. Irradiated skin in the
chronic stage is thin, hypovascularized, extremely
painful, and easily injured by any slight trauma or
infection. 399,401
Skin reactions to radiation should be treated early
to prevent complications later. Keeping the skin
moist and pliable to prevent fissures and cracks and
free of infection is extremely important. Mendelsohn
et al 402 has compiled a list of products to treat
radiation-induced skin changes (Table 10). If an
ulcer develops, the normal wound care protocols
should be initiated. In severe cases, wide
debridement and a skin graft or flap coverage may
be necessary.
Treatment with hyperbaric oxygen accelerates
healing in some patients, 403,404 but its effectiveness
in soft-tissue necrosis from radiation injury is
unproven. Experimental therapies include topical
TGF-β1, 405 granulocyte-macrophage colonystimulating
factor (GM-CSF), 406 orgotein (a Cu/Zn
chelate with superoxide dismutase), 407 topical vitamin
C, 408,409 topical corticosteroids, 410 glucorticoids,
411 NSAIDs, 412 aloe vera gel, 413,414 heliumneon
laser treatments, 415 and oral pentoxifylline
treatment. 416
HIGH-PRESSURE INJECTION INJURIES
High-pressure injection devices such as are used
for painting, cleaning, degreasing, etc. can produce
pressures of 600–12,000psi. 417,418 The substance
enters the skin through a seemingly insignificant
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